1. Field of the Invention
The present invention relates to a compressor, and particular to a novel kind ofsingle screw compress which can save power.
2. Description of the Prior Art
The techniques of single screw compressor have been improved gradually since the 1960""s, and the advantages of which, such as small vibration, low noise and high reliability, have been well acknowledged. Single screw compressors havebeen widely applied to industries performing as air compressors, processing compressors, air conditioners and thermal pumps and so on.
Both the screw and the pinion(s) of a single screw compressor may be of either cylindrical shape or plain shape in an outer profile, thus constituting four kinds of compressors of CC, CP, PC and PP types as shown in FIG. 2, in which the CP type compressor is the most popular and has been manufactured at a high volume.
FIG. 1 shows a conventional CP type single screw compressor which mainly consists of a screw 1, two pinions 2, a body 6, a spindle 3, a discharge port 4 and an inlet port 5. Generally, there are six screw threads and eleven pinion teeth. The number of screw threads varies with the compression ratio, the higher the compression ratio, the more the number of screw threads. FIG. 3 is a partially cutaway section view showing a mutual engagement of a screw of a conventional CP type single screw compressor with a pinion, in which the distance from the left generating line 8 to the rotating center of the pinion is the same as that of the right generating line 8, that is, the width of the left half pinion tooth and that of the right half pinion tooth are the same. Referring to FIG. 4, pinion tooth A has been engaged with the groove of the screw and the groove is closed completing the sucking process, while pinion tooth B is compressing the gas with a low pressure; and pinion tooth C has compressed the gas to a higher pressure to start the discharge process. Compared with other kinds, the CP type single screw compressor suffers one drawback in that the energy conservation is inferior especially when the discharge volume of the gas is small.
Theoretically, the specific energy requirement may be lowered and the discharge volume mat be increased if the diameter of the pinion of a CP type compressor is properly increased without changing any of the other parameters. The depths of the grooves of the screw may also be increased to correspond to the increase of the diameter of the pinion so that both the volume of the grooves and the discharge volume of the compressor may be increased. With these modifications, in order to keep the discharge volume constant, the diameter of the screw will have to be decreased so that the peripheral velocity of the same will be lowered, leading to a decrease of the viscous sheering loss caused by the lubricant filled between the screw and the body of the compressor. Moreover, the leakage passages will have to be correspondingly decreased and the volume efficiency of the compressor will also have to be increased, for the compressor is to conserve energy. However, the increment of the diameter of a pinion is restricted by the structure of the compressor in the conventional art. Referring to FIG. 5, the section of one groove of screw 1 engaging with pinion 2 (including pinion stand 7) cannot be beyond a half circumference, that is, the corresponding angle cannot be more than 180xc2x0. In order to ensure the rigidity of the pinion stand and the convenience of installation, the largest angle xcex82 that a groove could occupy equals (180xe2x88x92xcex81) when angle xcex81 the pinion and the pinion stand occupy in the cross section of the screw is determined. Referring to FIG. 3, xcex83 is the pinion""s largest work rotation angle, starting from the closing of the pinion tooth with a groove of the screw until the detachment of the pinion tooth. The relation between xcex82 and xcex83 is described in the following formula:
xcex83=xcex82xc3x97Z1/Z2
in which, Z1 stands the number of the screw threads and Z2 stands the number of the pinion teeth. FIG. 3 shows that the diameter of the pinion is the longest when xcex83 is at its maximum under the conditions of the conventional art.
It is noted that the compression and the discharge of the gas in the high pressure section are accomplished at the portion further away from the axis of the screw in FIG. 4. In that case, both the torque to the axis of the screw caused by the compressed gas and the work the screw requires for its reaction to the torque are strong. Correspondingly, both the torque to the axis of the screw caused by the compressor and the work the screw requires for its reaction upon torque are also strong. Therefore, the energy consumed in a conventional compressor is very high.
An object of the present invention is to provide a novel single screw compressor with improved energy conservation to overcome the above-mentioned drawbacks in the conventional art.
According to the present invention, a single screw compressor comprises a spindle, a body, a screw and two pinions. The respective distances from the left and the right generating lines of a pinion tooth to the axis of the screw are modified so that they are not the same. That is, the width of the left half of each of the pinion tooth does not equal to that of the right half of the pinion tooth. The modified pinion teeth are referred to as unequal-width pinion teeth to distinguish them from the equal-width pinion teeth in the conventional art. The teeth of the screw are therefore unequal-width teeth. The preferred range of the closing angle (xcex85+xcex94xcex8) of the compressor according to the present invention is from 60xc2x0 to 66xc2x0. According to the present invention the diameter along the screw is varied in an outer profile.